Funds are requested, to develop within the Fred Hutchinson Cancer Research Center a multidisciplinary breast cancer research program, named the Seattle Breast Cancer Research Program. The purpose of the program will be to stimulate innovative multidisciplinary research designed especially to provide a greater understanding of the factors that influence normal mammary epithelial cell growth and regulation, tumor promotion, and progression of existing carcinomas. It is assumed that such knowledge will lead to methods of primary prevention, and to improved methods to identify precancerous and early neoplastic lesions and hence also to better methods of secondary prevention and treatment. These purposes will be achieved by enhancing communication and collaboration among investigators in multiple fields through seminars, retreats, and joint pilot projects, and through the identification of needs for the recruitment of additional investigators from disciplines not adequately represented currently in our cancer center. A unique feature of our center is the strength of existing population-based resources and research. Another major strength is the quality and diversity of existing laboratory-based investigations at the cellular and molecular level in both human and non-human systems. Through the proposed program activities we propose to strengthen existing links and develop new collaborative studies that bridge these two general investigative areas, and focus these efforts on studies of breast cancer. Our ability to conduct studies in multiple defined populations will enhance the validity and applicability of our results to other setting. In addition, access to clinics that serve women with or at high risk of breast cancer will provide opportunities for translational activities to clinical problems. Plans and an institutional commitment to sustain this program on a permanent basis are described.